Many television stations now have available access to the National Weather Service radar displays.
In one prior art system, the weather radar scope is scanned by a television type camera, digitally converted into an audio signal which is transmitted over a telephone line to a television station where they are received and stored in a random access memory. This memory is then scanned electronically to form a television picture. The various intensity levels recorded in the memory may be represented by different colors on the viewer's television screen.
In another prior art television system, radar video information is digitized and stored in an electronic memory. The entire contents of that memory are then transmitted over voice-grade telephone lines to a television station where they are received and stored in another electronic memory which is then interrogated and only those signals necessary to form a television-compatible signal are used by the television station. Since the entire weather picture is recorded, and transmitted in its entirety over the telephone lines, this device requires a substantial memory and considerable time for the radar picture to be transmitted and then presented as a television picture.
The National Weather Service radar employs a rotating antenna through which pulses of radio frequency energy are transmitted at a repetition rate selected according to the range of the system. By way of example, a radar observing weather conditions within a 150 mile radius might use a pulse repetition rate of 164 pulses per second from an antenna which makes a complete revolution in twenty seconds, and therefore there will be 3280 radials extending from the antenna. A cathode ray scope displays the received information visually in a polar coordinate format on a plan position indicator scope.
It would be desirable if the video weather information received by the radar could be connected directly to the telephone line and sent to the remote location without requiring an additional scanning device; however, it is also important to avoid transmitting unwanted or unneeded information in order to conserve transmission time and bandwidth.